text: #!/usr/bin/env python3
  
  # Copyright (C) 2013-2014 The python-bitcoinlib developers
  #
  # This file is part of python-bitcoinlib.
  #
  # It is subject to the license terms in the LICENSE file found in the top-level
  # directory of this distribution.
  #
  # No part of python-bitcoinlib, including this file, may be copied, modified,
  # propagated, or distributed except according to the terms contained in the
  # LICENSE file.
  
  """Make a boostrap.dat file by getting the blocks from the RPC interface."""
  
  import sys
  if sys.version_info.major < 3:
      sys.stderr.write('Sorry, Python 3.x required by this example.\n')
      sys.exit(1)
  
  import bitcoin
  import bitcoin.rpc
  
  import struct
  import sys
  import time
  
  try:
      if len(sys.argv) not in (2, 3):
          raise Exception
  
      n = int(sys.argv[1])
  
      if len(sys.argv) == 3:
          bitcoin.SelectParams(sys.argv[2])
  except Exception as ex:
      print('Usage: %s <block-height> [network=(mainnet|testnet|regtest)] > bootstrap.dat' % sys.argv[0], file=sys.stderr)
      sys.exit(1)
  
  
  proxy = bitcoin.rpc.Proxy()
  
  total_bytes = 0
  start_time = time.time()
  
  fd = sys.stdout.buffer
  for i in range(n + 1):
      block = proxy.getblock(proxy.getblockhash(i))
  
      block_bytes = block.serialize()
  
      total_bytes += len(block_bytes)
      print('%.2f KB/s, height %d, %d bytes' %
              ((total_bytes / 1000) / (time.time() - start_time),
               i, len(block_bytes)),
            file=sys.stderr)
  
      fd.write(bitcoin.params.MESSAGE_START)
      fd.write(struct.pack('<i', len(block_bytes)))
      fd.write(block_bytes)
  